Which fuel pump and filter do our cars use?

ng8264723 · #1 (**permalink**) 06-06-2015, 08:26 AM

I have very low fuel pressure and I was going to order a new filter and pump. o when I take it apart if the filter doesn't fix it I will change the pump. The car has 2000 miles on it but I can't get it above 2.5 lbs and I even double checked with a mech gauge

lippy · #2 (**permalink**) 06-06-2015, 12:35 PM

They are all different. You need to see if you have a mechanical pump or an electric one. It shouldn't be worn after only 2000 miles, so it may be a regulator issue or something else.

mickmate · #3 (**permalink**) 06-06-2015, 08:28 PM

I'd be more concerned about flow than pressure. Does it seem like it's running out of gas? What pump is it, is there a regulator and how do you know pressure gauge is correct?

ng8264723 · #4 (**permalink**) 06-07-2015, 07:00 AM

I used a mechanical gauge it is correct. At 2.5 PSI the pressure is definitely wrong. I'm using whatever elec pump they put in and whatever filter they put in. It has a Mallory regulator as they recommend. There is nothing wrong with the regulator it is painfully simple

mickmate · #5 (**permalink**) 06-07-2015, 01:53 PM

The pump will have a name, color, model number to identify it. Is it only one electric or is it plumbed for a reserve with another pump? Is it feeding a single quad Holley? 5 psi should be a good number but what is the problem with it?

maurice19 · #6 (**permalink**) 06-07-2015, 09:42 PM

The fuel pump the Kirkhams used on #318 is Holley red electric.

I wrote down a number back in04 or 05 for it. 80615aa.

I remember that it has a built in reg, looks like a little screw on the top from my old drawing.

Best to google it for more accurate info.

Maurice

FatBoy · #7 (**permalink**) 06-18-2015, 03:04 AM

#523 also has a Holley Red Top, which I believe is their standard fitment. It has a built in regulator, so it doesn't need a separate one. There will probably be an inline filter just in front of the pump, which is mounted on the main chassis tube just to the right of the diff. Disconnect and remove the filter and clean it out. It will be obvious if it is blocked with debris.

Are you also using a mechanical pump on the engine?

Paul

Sandwich · #8 (**permalink**) 06-18-2015, 06:41 PM

Do you have a fuel regulator? the fuel pressure should be only about 4-5 psi.
Sorry, i read the rest of the posts.
I assume you've adjusted the regulator tighter?

ng8264723 · #9 (**permalink**) 06-23-2015, 12:17 AM

I have the recommended Mallory regulator with a return line. The pressure goes to 2.5 max! It was working fine this developed last season. I'm not sure why. I am going to pull the fuel filter. Can you clean it? Or is there a replaceable cartridge?

FatBoy · #10 (**permalink**) 06-23-2015, 05:09 AM

If it's the same as the one fitted to my car, you can dismantle it and clean it.

The Holley Red Top runs at a pre-set at 7psi and doesn't require a separate regulator according to their website.

I've since replaced the Holley with a pair of original SW240 pumps mounted in the trunk.

Paul

ng8264723 · #11 (**permalink**) 06-23-2015, 08:00 AM

The best way to run the a fuel system is with a return line. I did that an added the Mallory regulator that they recommended

FatBoy · #12 (**permalink**) 06-23-2015, 09:31 AM

Quote:

Originally Posted by ng8264723

The best way to run the a fuel system is with a return line.

Why?

ng8264723 · #13 (**permalink**) 06-23-2015, 03:28 PM

With a return system, the base pressure is set with the engine off, but the pump running. For a GM, this pressure is usually set to 58psi (factory fuel pressure in the rail). The vacuum/boost referenced regulator will help to change the pressure in the rail based on the pressure in the manifold. When an engine is idling, it may be pulling 20 inHg of vacuum, which translates to roughly 10psi. The reference to the regulator will allow it to adjust and lower the pressure in the rail to 48psi, resulting in 58psi effective pressure, which is the same as the base pressure. When the engine is making 10psi boost, the regulator will adjust and increase rail pressure to 68psi, again resulting in 58psi of effective pressure. The regulator will constantly bleed off pressure inside of the rail to maintain the same effective pressure at all operating conditions. This helps to prevent a loss of effective pressure during wide open throttle, and also helps to prevent injectors from having to run extremely low pulse widths to fuel at idle. A downfall of return systems is the fact that they circulate fuel through a very hot engine bay, ultimately carrying that heat back into your fuel tank.

A return style system that isn’t variable will maintain a certain pressure inside the rail, regardless of what is happening in the manifold. For instance, take a GM system with the standard 58psi in the rail (usually there is a mechanical regulator near the pump to bleed pressure back into the tank and keep the rail itself at 58psi). No matter what operating condition (short of demanding more fuel than the pump can supply), pressure in the rail will always be 58psi (or pretty close). When idling at 20 inHg, this means effective pressure will rise to 68psi because the vacuum in the manifold is adding 10psi to the rails 58psi. This requires injectors to pulse shorter so as to not overfuel the engine and cause a rich condition. By contrast, when a naturally aspirated engine is wide open throttle, the manifold pressure is not in vacuum or in boost, so the effective pressure is the 58psi of rail pressure and nothing more. However, a boosted engine at 10psi will be resisting the fuel, causing effective pressure to drop to 48psi from the 58psi in the rail. This lowers the ultimate output of the injectors

lippy · #14 (**permalink**) 06-23-2015, 04:03 PM

If you don't use a return one and regulator, you will be run by the pump in a "dead head" configuration and your pump will fail much sooner.

Morris · #15 (**permalink**) 06-23-2015, 04:40 PM

Quote:

Originally Posted by lippy

If you don't use a return one and regulator, you will be run by the pump in a "dead head" configuration and your pump will fail much sooner.

Vapor Lock.....

Size of the return line will effect the overall pressure.....

FatBoy · #16 (**permalink**) 06-23-2015, 11:52 PM

I was assuming from the very low pressure mentioned at the start that we're talking about a carbureted fuel system, not injected, is that not the case?

I'm happy to acknowledge that a return line is needed for an injected system, but not with a carb.
I also don't readily accept the argument that a fuel pump will fail sooner in. "dead head" setup. Pumps like the Holley Red are designed to run that way.

Paul

Sandwich · #17 (**permalink**) 06-24-2015, 12:49 PM

We run the return line to prevent vapor lock. If the fuel is circulating in the system, it has less time to get hot from the intake manifold.
Anyway, the pump could have failed. The Holley pumps we use have a small screen type filter before the impeller. Some times that can get clogged with junk, and prevent proper flow. Also, there is a bypass built into the pumps. There is a spring in the pump that sometimes we have to stretch it out to increase the pressure from the pump

ng8264723 · #18 (**permalink**) 06-27-2015, 10:42 PM

Sandwich,
I'm not sure what fixed it. I took the line off the filter. Since the tank had gas in it gas shot out. I had a plug ready for the AN line but some leaked on the floor. I took the filter out and cleaned it with brake cleaner. I put it back in and then was able to adjust the fuel pressure to 5 PSI. I do have a big problem that I need help with. Since I bought the car my fuel pressure has never worked. It is always pegged at 15PSI. I adjust the FP with a mechanical gauge. I have tried 2-3 fuel pressure senders and two gauges. It has to be the wiring. I need some help!